Production of propylene and aromatic compounds from liquid feed streams

ABSTRACT

Propylene and aromatic compounds are produced in significantly higher yields from liquid hydrocarbon feed streams by subjecting the feed stream to a low severity thermal cracking process. The effluent from the low severity thermal cracking process is separated into a stream comprising C8 and lighter components and a stream containing the C8 and heavier components. The stream containing the C8 and heavier components is thereafter subjected to a thermal hydrocracking process.

United States Patent 1 Downs et al.

1 51 Jan.30, 1973 154] PRODUCTION OF PROPYLENE AND AROMATIC COMPOUNDS FROM LIQUID FEED STREAMS [75] Inventors: Ronald 0. Downs, St. Louis, Mo.; Robert M. Engelbrecht, deceased, late of St. Louis, M0. by Alice M. Engelbrecht, executrix; James C. Hill, Chesterfield; Richard N. Moore, St. Louis, both of Mo.

[73] Assignee: Monsanto Company, St. Louis, Mo.

[22] Filed: July 9,1970

[21] Appl. No.: 53,692

[52] US. Cl. ..260/673.5, 208/68, 208/76, 260/683 R [51] Int. Cl ..C07c 3/30 [58] Field of Search ..208/48 Q, 68, 76; 260/672 NC, 260/673.5

[56] References Cited UNITED STATES PATENTS Moy et a1. ..260/673.5

3,240,831 3/1966 Cottington ..208/68 3,329,735 7/1967 Paul et a1 ..260/6735 3,076,046 1/1963 Estes et a1. .,260/673.5 3,265,612 8/1966 Dulaney ct al. ....26()/673.5 3,271,298 9/1966 Duluncy ct ul. ..260/6735 Primary Examiner-Curtis R. Davis Attorney-Thomas B. Leslie, Richard W. Sternberg and Neal E. Willis [57] ABSTRACT 10 Claims, No Drawings PRODUCTION OF PROPYLENE AND AROMATIC COMPOUNDS FROM LIQUID FEED STREAMS BACKGROUND OF THE INVENTION ethylene, propylene and aromatic compounds from liquid hydrocarbon feed streams.

Many processes are known in the prior art for converting liquid hydrocarbon feed streams, such as crude petroleum and similar materials derived from carbonization deposits of ancient origin into various valuable hydrocarbon components. In recent years, a great number of processes have been developed that require such hydrocarbon components as ethylene, propylene and aromatic compounds including benzene, toluene, xylenes and the like as raw materials. Thus, various methods have been derived for obtaining these valuable components from hydrocarbon feed streams. One particular method that has been widely used for producing ethylene, propylene and aromatic compounds from hydrocarbon feed streams is by subjecting the hydrocarbon feed streams to a high temperature thermal pyrolysis, otherwise known as thermal cracking. It has been found that the thermal cracking of various hydrocarbon feed streams will produce ethylene, propylene and other valuable components such as aromatic compounds therefrom. It has been widely accepted in the petroleum industry that maximum ethylene, propylene and aromatics production is achieved by subjecting the hydrocarbon feed streams to a high severity thermal cracking process. The high severity thermal cracking processes do in fact produce large quantities of ethylene, but undesirable products such as low value pitch and other low value products are produced along with the ethylene. Generally, it has been found that propylene is produced in smaller quantities as the severity of the thermal cracking is increased.

In view of the desirability of minimizing the production of pitch and maximizing the production of propylene and aromatic compounds from hydrocarbon feed streams, it is highly desirable that new processes be developed for achieving such results in overall production from the treatment of hydrocarbon feed streams.

SUMMARY OF THE INVENTION We have discovered an improved process whereby liquid hydrocarbon feed streams can be converted into valuable products in improved quantities while greatly reducing the quantities of pitch concurrently produced. Briefly stated, our invention comprises the steps of subjecting a liquid hydrocarbon feed stream to a low severity thermal cracking process. The effluent produced by this thermal cracking process is then very simply separated into two fractions, the first fraction contains C and lighter components, from which the ethylene and propylene can be recovered. The second stream contains the C and heavier components. This second stream is subjected to a hydrocracking process wherein aromatic compounds and other valuable hydrocarbon materials are produced. By carrying out our invention, the products obtained from the thermal process are far more valuable than the original hydrocarbon feed stream. Our invention provides for the production of very valuable hydrocarbon components, including propylene and aromatic compounds, in yields that are greater than yields obtained in conventional hydrocarbon conversion processes.

DESCRIPTION OF PREFERRED EMBODIMENTS Our invention is useful in the conversion of various liquid hydrocarbon feed streams to more valuable hydrocarbon products such as ethylene, propylene, aromatic compounds and diolefin compounds, without the production of high amounts of undesirable products such as pitch and residue material. The liquid hydrocarbon feed streams that can be utilized in our invention include various materials such as oil field condensate, crude petroleum, gas oil and naphthas obtained from various other petroleum conversion processes, and the like. The liquid hydrocarbon feed streams can have an initial boiling point within the range of 60 to l,100F. and may contain dissolved gases such as ethane and methane. The more preferred liquid hydrocarbon feed streams are those that have a final boiling point of from 850 to 1,050F. and that are essentially free from asphaltine components. While the liquid hydrocarbon feed streams are preferably free from any contaminants such as sulfur, sulfur-containing compounds, nitrogen-containing compounds and the like, certain quantities of such contaminants can be present in the liquid hydrocarbon feed stream. When such contaminants are present, it is desirable that they be present in no more than about 2 weight percent of the hydrocarbon feed stream. If the desired hydrocarbon feed stream contains higher amounts of such contaminants, they can be removed prior to carrying out our process.

In carrying out our invention, the liquid hydrocarbon feed streams defined above are first subjected to a low severity thermal cracking process. Such a process is carried out in a conventional tubular reactor that is commonly known as a cracking furnace. The hydrocarbon feed stream is allowed to flow through the heated cracking furnace thereby heating the feed stream to a temperature whereby the hydrocarbon feed stream is decomposed into various hydrocarbon components including ethylene, propylene, various diolefins and other materials. In contrast to prior art methods for thermally cracking hydrocarbon feed streams, our invention is based on a low severity thermal cracking of the hydrocarbon feed stream. In other words, we do not crack the hydrocarbon feed stream to an excessive degree as now done in many commercial processes. In defining cracking severity, we utilize a value that is obtained by taking the ratio of the ethylene produced in the cracking process to the propylene producedin the cracking process. We define this ratio as the cracking severity. Thus, for example, if 1.5 pounds of ethylene were produced by cracking 10 pounds of a hydrocarbon feed and 1 pound of propylene was also produced, the cracking severity would be 1.5. Thus, as the material is more severely cracked in a thermal cracking process, more ethylene will be produced in relation to the propylene that is also produced. In our process, it is necessary that the cracking severity be no greater than 1.5, and preferably from about 1.2 to 1.4. We have found that if the cracking severity is higher than 1.5, undesirable results are obtained. We have found that the amounts of low value methane and pitch increase and the ultimate yield of such valuable materials as C aromatic compounds and propylene are reduced. Furthermore, the resin and pitch produced are less amenable to hydrocracking since they produce higher quantities of coke and other solids.

The operating conditions for the thermal cracking step can be rather widely varied so long as the cracking severity as defined above is maintained at a value no greater than 1.5. Thus the pressures can range from to 100 psig, but preferably from about 5 to 40 psig. The liquid hourly space velocity will generally range from about 50 to 1000 and preferably from about 150 to 500 pounds per hour per cubic foot. The chief condition controlling the cracking severity in a thermal cracking operation is that of temperature in the cracking zone of a cracking furnace. lt is present practice to carry out such thermal cracking at temperatures ranging from 750 to 850C. and preferably in the upper part of this temperature range. However, we

have found that superior results in the yields of the 1 most valuable materials are realized if the cracking is carried out at temperatures wherein the ethylene to propylene ratio in the effluent stream produced is not greater than 1.5, and generally temperatures in the range of 700 to 820C. are required for such low severity cracking. Preferably, the temperature will range from about 750 to 800C. in the thermal cracking zone.

The pattern of materials produced by a thermal cracking operation will vary not only with the cracking condition employed but also with the nature of the feedstock cracked. For purposes of illustration reference will be made to typical cracking patterns for petroleum condensate feedstocks, but the relative changes in product pattern will not be widely different for other of the suitable feedstocks described above. Subjecting a typical petroleum condensate feedstock to a high severity thermal cracking of 1.5 to 1.6 generally results in a pattern of products with the following major component groups as percentage of the effluent:

Gases H and CH -16 C, C HC 49 C, C,,HC 21 C C HC 6 Heavy Ends 9-10 Gases H, and CH 14 C, C,HC 54-55 C, C HC 19 C. C HC 5 Heavy Ends 7-8 Thus, the lower severity thermal cracking results in increased production of the desirable C to C: hydrocarbon materials, both saturated and unsaturated, and in decreased production of the less valuable gases and heavy ends. However, the particular advantage of cracking at low severity is that the products thereof boiling from about C are more susceptible to upgrading by the hydrocracking step. Thus, the overall yields of desirable products are higher when low severity thermal cracking plus hydrocracking is compared with high severity thermal cracking plus hydrocracking.

The increased production of other desirable products including propylene and aromatic hydrocarbons is realized by the present novel process which involves separating a product fraction of C and heavier components and subjecting such fraction to a thermal hydrocracking process. This latter process results in substantially increased yields of useful and valuable olefins and aromatic compounds as well as substantially lower yields of the low value pitches and resins.

It might be assumed that the same improved yields could be realized byseparating and hydrocracking a C and heavier fraction resulting from a high severity thermal cracking process. However, contrary to any such assumption this has not proved to result in fact. Not only does the high severity cracking result in increased yields of heavy ends, designated as resin oils and pitch resins, but these increased amounts of heavy ends have been found to be very refractory in that they produce relatively large amounts of solid decomposition products or coke which tend to plug subsequent reactors and to be generally unsuitable for further processing such as hydrocracking. Thus, not only does the lower severity cracking such as to produce an ethylene to propylene product ratio of not greater than 1.5 result in lower yields of such heavy ends, but in heavy ends which are most suitable for further processing by thermal hydrocracking to produce high yields of valuable aromatic compounds and much reduced yields of heavy ends from the hydrocracking process.

The step of separating the effluent from the low severity thermal cracking process into its two major fractions of C and lighter components and C and heavier components is readily carried out in conventional distillation apparatus such as a distillation tower or towers. It is only essential that such equipment be capable of making a separation between the two major product fractions in the effluent from the thermal cracking process.

In any thermal cracking process a separation into two or more fractions is carried out on the effluent from such process. In a typical thermal cracking process a quenching of the effluent is carried out immediately after the effluent is transferred from the cracking furnace. In many of such processes the step of quenching the cracked effluent to prevent further undesired cracking is accomplished in a tower which utilizes the heat in the cracked effluent to effect a first gross separation of the effluent into two or more fractions, though the two operations can be carried out separately. In the present novel process the first gross separation of cracked and normally quenched effluent is carried out in such a manner as to produce the two product fractions described above. In contrast to many present processes which carry overhead all products designated resin oil and lighter, i.e., those boiling up to a temperature of about 220C, the pressure and temperature conditions in the distillation tower or towers are maintained so as to yield an overhead product fraction composed of C and lighter components, i.e., those boiling up to a temperature of about 156C.

The overhead product fraction of C and lighter components is further separated into its constituent compounds and narrow fractions according to conventional processes and in conventional manner all of which processes are well known. The heavier product fraction of C and heavier components is then subjected to hydrocracking in accordance with the present novel process.

According to the present process the C and heavier fraction of cracked and quenched effluent is subjected to a thermal, non-catalytic hydrocracking process. This thermal hydrocracking is carried out at temperatures within the range of 650 to 800C. and at pressures of from l to 2,000 psig. The preferred temperature range for the hydrocracking is from 700 to 770C. and the preferred pressure range is from about 150 to 1,000 psig. The residence time in the thermal hydrocracking reactor can be within a range of to 100 seconds and preferably is in the range of 10 to 60 seconds. The ratio of hydrogen to hydrocarbon fraction hydrocracked can range from 0.5 to moles of hydrogen per l00 grams of hydrocarbons, but preferably is in the range of 2 to 10 moles/lOOg. The source of the hydrogen for use in the hydrocracking reaction is not critical but such hydrogen stream can be derived from a hydrogen generating plant or from by-product streams rich in hydrogen, i.e., which contain at least 50 mole percent of hydrogen. Such stream can also contain up to 50 percent other gases inert to the hydrocracking conditions such as nitrogen, carbon dioxide, carbon monoxide and the like. Preferably such a by-product hydrogen rich stream will contain at least 75 mole percent hydrogen.

The hydrocracked effluent from the hydrocracking process is separated and subjected to recovery operations in known manner according to conventional processes. Thus, the portion of hydrocracking effluent containing the C and lighter components can be joined with the same fraction separated from the thermal cracking effluent and further separated into its constituent compounds and narrow fractions by the same processes. The remaining smaller amounts of C aromatic compounds, alkyl naphthalenes and resin oil can be recovered by conventional processes for recovery of these product streams. Alternatively, these heavier fractions can be recycled for further hydrocracking along with the C and heavier fraction from the thermal cracking process. The greatly reduced amount of resin PR present in the hydrocracked effluent can also be recycled to the hydrocracking process but normally is disposed of as that product. The great reduction in the amount of such low value resin or pitch product is one of the distinct advantages realized from the present process.

To further illustrate the present invention as well as to demonstrate its operation the following examples are set forth as illustrative only and not limitative.

EXAMPLE I Samples of a petroleum condensate having a final boiling point of approximately 900-920F. were thermally cracked under varying conditions of severity and the products thereof collected and analyzed. The liquid product fractions of the thermal cracking operations were then distilled to remove as overhead all products boiling up to 156C. and the remaining fractions of C and heavier components from each thermal cracking were thermally hydrocracked under the same conditions. The products from the thermal hydrocracking were collected and the amount of each individual component were determined analytically. Based upon the weight of C and heavier fractions submitted to hydrocracking the yield of each product was determined and from these results the overall yields of each product or product group from both steps were determined.

The thermal cracking step was carried out in a bench scale cracking reactor which consisted of a inch alloy tube of 0.305 inch internal diameter bent into six parallel sections and electrically heated. Cracking occurs in the final two-thirds of the cracking tube where the temperature profile is approximately linear rising from about 500C. to the outlet temperature, which is controlled at from 760 to 800C. and operating at a total pressure of 40 psig. The charge to the thermal cracking unit contained approximately 0.27 by weight of steam and the liquid hourly space velocity of throughput of the total feed was maintained at 255 lb./hr./ft. The steam and petroleum condensate were metered into the reactor. The effluent was quenched, collected and analyzed by gas chromatography to determine the yields of products. A sample was distilled to determine the yield of pitch, designated Resin PR.

The cracked oils recovered from each of the above runs at 760, 775 and 800C. outlet temperatures were distilled under vacuum to remove all of the C and lighter components and remaining product fraction of C and heavier components was subjected to a thermal hydrocracking. This product fraction was made up of cuts denominated C aromatics, resin oil, alkyl naphthalene concentrate and resin PR, i.e. pitch and resin. The hydrocracking step was carried out in a bench scale hydrocracking reactor which consisted of an 8 54 inches alloy tube of 1 V1 inches outside diameter with a inch internal bore, the entire tube electrically heated and the temperature recorded at approximately the mid point of the length of the reactor. The hydrocarbon oils were charged from a 10 ml. burette through a dripping feed inlet tip which was surrounded by a cooling water coil onto the pebble packing. The reactor was packed throughout with approximately 10 ml. gross volume of heat exchange pebbles which provided approximately 5 ml. of effective reactor volume. At the pressure of 700 psig the residence time was approximately 20 seconds. The temperature employed was 730C. and the feed consisted of 0.1 gram of cracked heavy oil fraction and 7 millimoles of hydrogen per minute. Time for each hydrocracking run was recorded as well as the time before the cracked heavy oil fraction resulted in plugging of the hydrocracking reactor where such plugging occurred.

The results of three thermal cracking runs at increasing outlet temperatures of 760, 775 and 800C. and

increasing severity as indicated by ethylene/propylene ratios of 1.27, 1.32 and 1.46 respectively, together with the results of thermally hydrocracking the C and heavier fraction from each of the thermal cracking runs plugging of the small reactor with coke in run C indicated a heavy end fraction which was severely cracked and not entirely suitable for subsequent hydrocracking. There were also increases shown in the are set out in Table 1 below. The respective cracking yields of propylene, butadiene, total C hydrocarbons, steps were conducted in the reactors and under the and with an increase of to percent in the ethylconditions described above. In each case the portion of benzene, xylene and styrene fraction, all desirable and the product from thermal cracking which was subvaluable products. In addition, the alkyl naphthalene jected to hydrocracking is bracketed in the table below, concentrate, wh|ch also included the naphthalene The results are indicated in terms of weight percent 10 pr du d contained a much higher percentage of yield of each component or group of components as naphthalene after hydr cracking. determined by gas chromatographic analysis.

TABLE 1 Thermal Hydro- Thermal Hydro- Thermal Hydrocracking cracking cracking cracking cracking cracking Temp.profile, C 500-760 730 500-775 730 500-800 730 Pressure, p.s.i.g 40 7 40 700 40 100 LHSV or res. time 255 1 20 255 1 20 255 1 20 Steam/HG or HQ/HC 0. 27 7/1 0. 27 7 0. 27 7 1 Severity, E/P 1. 27 1. 32 1. 46 Time of run, hours 2. o 2 1.3

Com onent ie1d,weight percent:

L I 0.48 0.48 0. 52 0.52 0.68 12.46 16. 10 13. 58 17. 44 15. 0. 09 0.00 0.11 0.11 0.16 16. 70 16. 83 17. 46 17. 52 18. 82 4. 52 6. 48 4. 52 7. 28 4. 63 1.10 1. 28 0. 08 1.10 0. 73 13. 22 13. 22 13. 20 13. 20 12. 89 Butadiene 2. 53 2. 53 2. 50 2. 50 2. 38

Total C. 8.58 8. 60 7. 64 7. 64 6.03 Me acetylene. 0. 41 0.41 O. 36 0.36 O. 25 Total 05 2.87 2. 87 2. 01 2. 01 3.06 Paraflins and naphthenes 7. 64 7. 64 3. 82 3. 82 1. 86 CFC; unsaturates 0.43 0.43 0.41 0. 41 Benzene 7. 22 8. 22 9. 13 10. 36 9.20 Toluene 5.30 6.41 6. 29 7.43 5.55 Ethylbenzene, xylene and styrene. 4. 74 5. 24 4. 10 4. 77 4. 22

Resin oil 4.63 0. 4. 51 0.67 Alkyl naph. conc- 3. 44 3. 28 3. 83 4. 28 Resin PR 5. 46 1. 71 6. 78 1.24

Total hydrocracked 13. 53 15. 12

1 Seconds. 2 Plugged. 3 Plugged less than 1 hour. No sample.

It is seen from Table 1 that by subjecting to 4() hydrocracking the C and heavier fraction from the initial thermal cracking there are much smaller amounts of resin oil and resin P R produced, resin oil being reduced by almost 90 percent and resin PR to from one-third to one-fourth the original amount. The

EXAMPLE 11 Additional samples of the same petroleum condensate were thermally cracked and the C and heavier fractions from each run then hydrocracked under substantially the same conditions and in the same equipment as in Example 1 above. The cracking conditions and the results of each run are set out in Table 11 below.

TABLE II D E F Thermal Hydro- Thermal Hydro- Thermal Hydroeracking cracking cracking cracking cracking cracking Temp. profile, C 500760 730 500-775 730 500-800 730 26 7 40 700 26 700 319 l 20 315 1 20 318 1 20 0. 27 7/1 0. 27 7/1 0. 27 7/1 1.26 1.30 1.58 2 4. 1 9 1 2 8 0. 0. 35 0. 39 0. 39 0. 52 O. 52 9. 11. 53 11. 12. 45 12. 64 14. 44 0. O. 06 0. 1O 0. 10 O. 20 O. 20 16. 16. 33 17. 38 17. 41 19. 95 19. 98 3. 5. 34 4. 53 5. 03 3. 79 4. 73 O. O. 30 0. 34 O. 34 0. 32 0. 32 Propylene 12. 12. 92 13. 39 13. 39 12. 61 12. 62 Propane 0. 1. 59 0. 89 1. 06 0. 66 0. 91 11111111110110 2. 2. 45 2. 45 3.09 3.09 'lolnl (4 1' 12. 99 12. 11 12.13 10. 39 10. 42 'lninl 1 1 3. 55 3. 29 3. 29 2. 63 2. 63 l'wrnllim :md nuphlhunc 8. 88 4.18 4. 23 4. 64 4. 66 (.4 unsnlurnles 1.14 1.57 1.57 0.31 0.31 lh'lm'ne 6. 92 7.17 7. 69 7. 91 8.42 'loluunv 1 5. 67 5.15 6. 14 4. 83 5. 85 |-Ztl\ \'llwu2v|n-. xylene nud styrene. 5. 6S 4. 30 5. 34 4.12 5.14

( m'muntlt's 1 1 0. 0 0. 53 ltvsln oll. 4. .61 1.13 3. 50 1. 38

TABLE it D E F Thermal Hydro- Thermal Hydro- Thermal Hydr; cracking cracking cracking cracking cracking cracking Alkyl naph. conc 4. so 3.11 4.11 3. 31 4. 57 4. 05 Resin PR 4. 68 2.15 5. 33 2. -1 5. 03 2. 73

Total liydrocrackcd 15.00 13 61 Material unaccounted for 0. 13 1 Seconds. 1 Plugged.

It is seen from Table 11 that the ields of heavy ends d. recoverin eth lene, ro lene and aromatic com- Y E y P P) as re resented b resin oil and resin PR were reduced ounds from said first fraction and said h dro- P y P Y to one-third or less in the case of resin oil and to less cracked second fraction. than one-half in the case of resin PR by the 2. The process of claim 1 wherein the thermal hydrocracking process step. The rapid plugging of th 15 cracking process IS carried out at a temperature of up O small reactor with coke in Run F indicated that the to 820 C and 313 pressture "P to p severe cracking to an ethylene/propylene ratio of 1.58 f P f of clam 1 wherem the hydrocrackmg produced a heavy end fraction not as Suitable f process 15 carried out atatemperature of650to 800C. hydrocracking as those from the lower severity thermal and at a Pressure of 100 P cracking runs. There may also be noted increases in the 20 The P of f 3 wherem ratlo f yields of propylene total C and total C5 hydrocarbons hydrogen to hydrocarbon 1n the hydrocrackmg zone and with an increase of up to 10 percent of the ethylfrosm to moles ge llQo grlams1 h h benzene, xylene and styrene fraction in Runs D and E e Proms? 0 9 w erem t e t erma when compared to Run F Showing the improved cracking process is carried out at a seventy to produce results achieved by the lower severity thermal cracking z sg igiigzfifii' to propylene of from to m the m a: ZR 5:2! two-stage process" 6. The process of claim 1 wherein the feed stream is a 1 An in'lproved process for producing ethylene petroleum condensate having a f1na1 boiling point of l d m nds from a H from 850 to 1050F. and essentially free from asphalpropy ene an aroma 1c co pou q tine components.

hydrocarbon feed stream comprising:

a. subjecting a feed stream having an initial boiling point within the range of 60 to l,l0OF to a noncatalytic thermal cracking process in a tubular cracking furnace of a severity to produce a ratio of 7. The process of claim 6 wherein the thermal cracking process is carried out at a severity to produce a ratio of ethylene to propylene offrom 1.2 to 1.4 in the cracked effluent.

8. The process of claim 6 wherein the thermal cracking process is carried out at a temperature of 750 to 800C. and at a pressure of 5 to 40 sigri 9. The process of claim 6 wherein e ydrocrackmg process is carried out at a temperature of 700 to 770C. and at a pressure of 150 to 1,000 psig.

10. The process of claim 6 wherein the feed stream to the thermal cracking process contains steam as an inert diluent. 

1. An improved process for producing ethylene, propylene and aromatic compounds from a liquid hydrocarbon feed stream comprising: a. subjecting a feed stream having an initial boiling point within the range of 60* to 1,100*F to a non-catalytic thermal cracking process in a tubular cracking furnace of a severity to produce a ratio of ethylene to propylene not greater than 1.5 in the cracked effluent produced, b. separating said cracked effluent into a first fraction comprising C8 and lighter components and a second fraction comprising C9 and heavier components, c. subjecting said second fraction containing the C9 and heavier components to a non-catalytic thermal hydrocracking process, and d. recovering ethylene, propylene and aromatic compounds from said first fraction and said hydro-cracked second fraction.
 2. The process of claim 1 wherein the thermal cracking process is carried out at a temperature of up to 820*C. and at a pressure up to 100 psig.
 3. The process of claim 1 wherein the hydrocracking process is carried out at a temperature of 650*to 800*C. and at a pressure of 100 to 2000 psig.
 4. The process of claim 3 wherein the ratio of hydrogen to hydrocarbon in the hydrocracking zone is from 0.5 to 20 moles per 100 grams.
 5. The process of claim 1 wherein the thermal cracking process is carried out at a severity to produce a ratio of ethylene to propylene of from 1.2 to 1.4 in the cracked effluent.
 6. The process of claim 1 wherein the feed stream is a petroleum condensate having a final boiling point of from 850* to 1050*F. and essentially free from asphaltine components.
 7. The process of claim 6 wherein the thermal cracking process is carried out at a severity to produce a ratio of ethylene to propylene of from 1.2 to 1.4 in the cracked effluent.
 8. The process of claim 6 wherein the thermal cracking process is carried out at a temperature of 750* to 800*C. and at a pressure of 5 to 40 psig.
 9. The process of claim 6 wherein the hydrocracking process is carried out at a temperature of 700* to 770*C. and at a pressure of 150 to 1,000 psig. 